Vermont Sen. Bernie Sanders said Thursday that a tax on soda proposed by Philadelphia’s mayor and endorsed by Hillary Clinton is “regressive.”

“It will be increasing taxes on low-income and working people and at a time of massive levels of income and wealth income inequality, our goal has got to be to ask the people on top to pay more in taxes and not working people,” Sanders told NBC Philadelphia of the three-cents-per-ounce levy proposed last month by mayor Jim Kenney.

“I think the mechanism here is fairly regressive,” he added.

Clinton holds an opposite view. At a campaign stop on Wednesday she said she was “very supportive” of the tax, which will double the cost of 2-liter bottles of soda and 12-packs of 12-ounce cans.

The revenue raised from the tax, which Kenney estimates will hit $400 million over the next five years, will be used to help fund universal prekindergarten education.